Actually withdrawing too much cash was one of the reasons cited in the article for banks closing down people's accounts ;)

Going off of this article at least, it can take a few weeks for a bank to either reopen your account or send you the balance. Having around a month's worth of emergency cash would make sense to be able to handle an account closure like this.

I am a firm believer of having 10% of ones liquid net worth in cash or equivalent not gatekept by anyone but myself.

This is from extremely hard won personal experience.

Yes, it's a lot of cash. I don't mean keep it all under your mattress.

One day, pirates learned they could get better interest on their treasure by putting it into banks than they could by burying it. But many had forgotten where they buried it and were not able to take part in this new world

I suppose the smart pirate would diversify their portfolio. Keeping it all the bank doesn't sound super smart for a pirate who might be unmasked and assets seized.

Certainly no form of wealth storage is without risks!